Glass, especially glass used in windows and doors, is ubiquitous in the modern world. Glass is an integral part of almost all buildings such as businesses, schools, hospitals, hotels and restaurants. Glass windows and doors are used to supply natural light and to provide visibility both into and out of structures. Unfortunately, having glass windows, especially if they entail large areas of glass, can cause some unwanted problems.
Glass windows and doors are a major entry point for break-ins and robberies. Additionally, glass windows are highly vulnerable to extreme weather and even blast effects form industrial accidents or terrorist activity. In particular, many window and door glasses are prone to shattering into countless number of potentially deadly shards of airborne pieces. One solution has been to utilize laminated, or so-called “safety” glass, which generally has a plastic layer laminated between two glass layers. Such laminated glass is very expensive, difficult to retrofit in many applications, and while it strengthens the glass portion of a window or door, does not increase the resistance of the glass portion to being blown out of its framing.
Another solution employed in past, especially in attempts to retrofit existing glass for greater safety, has been the addition of a polyester safety film. Such a film does not significantly change the propensity of glass to shatter into multiple pieces, but does a reasonable job in holding the glass fragments together in case of breakage. Such films are commonly know as “safety films” or “fragment retention films.” Holding glass shards together does improve the safety aspects, but especially does not necessarily produce a more secure environment. For example, it is not uncommon, after severe weather or a blast incident, to find that the entire window pane has been blown out of a window frame.
In the past, fragment retention films have often been anchored by means of double-faced tape strips with plastic backings, such as that taught by U.S. Pats. Nos. 5,992,107 and 6,931,799. The double-faced tape is employed to secure the strip to both the glass and the glass frame, and the plastic strip is employed to provide strength to the assembly. These assemblies are fraught with problems. Firstly, because the strip material that may be bonded to the glass is insufficiently strong, a flexible first strip material is generally bonded to a less-flexible second strip material for strength. This may produce adverse effects on flexibility. Secondly, prior art strips are generally, if not exclusively, taught as internal mounted fixtures, due to the weather-bearing inadequacies of the often-PVC strip materials. In additions, and corrected in an additional embodiment of the present invention, these adhesive strip devices lack a mechanical anchor to the window frame.
However, such adhesive-only, relatively inflexible, mounting assemblies are only as reliable as the film to strip adhesion, and the frame to strip adhesion. This can be a particular problem as surface conditions of the glass frame, such as roughness or low adhesion surfaces may intrinsically compromise safety. In addition, adhesive bonds are affected by such environmental parameters as temperature, and by expansion and contraction movement of the glass within the frame.
The instant invention addresses these, and other problems, in unique and effective ways, as are detailed below.